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Old 2021-04-29, 00:11   #562
Dr Sardonicus
 
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Quote:
Originally Posted by ATH View Post
Ryan Propper found another factor and another PRP #356: M3917
I'm curious. Usually when a cofactor tests as a PRP, the residue is listed as

PRP_PRP_PRP_PRP_

But here, although the history says the remaining cofactor is a probable prime, the PRP cofactor residue is a hex value with, I presume, the last few digits obscured pending confirmation...
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Old 2021-04-29, 01:05   #563
ATH
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Quote:
Originally Posted by Dr Sardonicus View Post
I'm curious. Usually when a cofactor tests as a PRP, the residue is listed as

PRP_PRP_PRP_PRP_

But here, although the history says the remaining cofactor is a probable prime, the PRP cofactor residue is a hex value with, I presume, the last few digits obscured pending confirmation...
Yeah, that is strange I had not noticed, since it was spamming my results.txt with PRP. It was on an AWS instance, and I only noticed it by coincidence, because I was upgrading it to 30.6b4.

Now I ran it again and unintentionally double checked my own result, now it shows as PRP. But PRP-CF usually do not have hidden or fake residues?
I'm not sure why it used type 1 PRP test, here in the 2nd manual test I specifically told it to do a type 5 test.

Someone else please double check it as well.

Last fiddled with by ATH on 2021-04-29 at 01:06
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Old 2021-04-29, 04:47   #564
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Quote:
Originally Posted by ATH View Post
Someone else please double check it as well.
Like Ryan's other recent factor discoveries, the factor got reported almost immediately to FactorDB (by Ryan himself?), and the cofactor is usually already certified prime there before the first PRP test completes on PrimeNet.

FactorDB link

Last fiddled with by GP2 on 2021-04-29 at 04:58
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Old 2021-04-29, 05:23   #565
LaurV
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Wow, 61 digits? That's a beast! Congrats Ryan!
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Old 2021-04-29, 11:14   #566
Dr Sardonicus
 
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A 61 decimal digit factor winkled out. Amazing!

Whatever the problem was with the PRP cofactor residue, it's been fixed. Two tests show a residue of PRP_PRP_PRP_PRP_

And, as previously noted, the cofactor is already certified prime. Another fully-factored Mersenne composite!
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Old 2021-05-20, 13:50   #567
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There are now 357 known Mersenne numbers with prime exponent that are composite and either fully factored or probably fully factored.

The most recent is M4021. Its final factor (66 digits) was found by Ryan Propper on 2021-05-19 and the PRP test was done by user "mnd9".

FactorDB link

The cofactor was already certified prime yesterday on FactorDB.
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